The present invention relates to a machine for inspecting the surface conditions of structural members within a furnace, particularly inside a furnace operating at a high temperature and/or with a highly radioactive environment, such as a melting furnace for radioactive wastes processing.
A view of the configuration of an inspection machine inside a vacuum chamber that was disclosed in Japanese Patent Laid-Open Publication No. Sho 60-169745 is shown in FIG. 6 as an example of the prior-art. In this prior-art, an image fiber 106 is used instead of an industrial television camera in a vacuum chamber 101 of a melting device. An arm tip part 105 capable of changing its protruding direction is attached to a lower end of a main arm portion 104 capable of moving up and down in an axial direction of a tubular structural member 103. Movable blocks capable of adjusting in the length are suspended from the arm tip portion 105, and an objective part 102 of the image fiber is mounted thereon.
This configuration is capable of withstanding a temperature of approximately 250.degree. C. within the vacuum chamber 101 and makes it unnecessary to provide the large cooling gas that would be needed if an industrial television camera system was inserted. Thus it provides an inspection machine that is far superior from the viewpoints of heat resistance, monitoring range, and ease of maintenance.
The above described prior-art made it possible to continuously monitor the interior of a vacuum chamber without requiring the use of large quantity of coolant for cooling, by using imaging portion of an image fiber that can withstand a temperature of approximately 250.degree. C. instead of an industrial television camera that can withstand a temperature of only about 60.degree. C., which had been used up until that time.
However, there are certain problems with the above described prior-art, as described below. The first problem concerns the inspection-hostile environment. When the object being inspected is a melting furnace for radioactive wastes processing or the like, the decay heat due to the high level of residual radioactivity can cause the interior of the furnace to reach a fairly high temperature of 400.degree. C. to 500.degree. C. However, the thermal resistance of the fiberscope is only about 250.degree. C., so it cannot be used without some form of cooling machine.
Further, since the various drive mechanisms of the inspection machine inserted into the furnace are exposed to high levels of radioactivity in addition to high temperatures, the components thereof have extremely short lifetimes and thus it is necessary to replace them after a short period of time. However, the inside of the melting furnace is a highly radioactive region, called a hot cell, so that this replacement of components must be performed by remote operation, and thus there are extreme restrictions on use.
Another problem concerns inspection method. Quantitative inspection is essential for purposes such as lifetime estimation, but the above described prior-art cannot be used for such purposes because it provides qualitative inspection by observation.